Re: [linux-sunxi] Re: [PATCH v3 1/2] drm/bridge: dumb-vga-dac: Support a VDD regulator supply

[Archit Taneja]

Hi,

On 11/15/2016 08:29 AM, Chen-Yu Tsai wrote:
> Hi,
>
> On Wed, Nov 2, 2016 at 9:33 AM, Chen-Yu Tsai <wens@xxxxxxxx> wrote:
> > On Mon, Oct 31, 2016 at 2:28 PM, Rob Herring <robh@xxxxxxxxxx> wrote:
> > > On Sat, Oct 29, 2016 at 07:06:10PM +0800, Chen-Yu Tsai wrote:
> > > > Some dumb VGA DACs are active components which require external power.
> > > > Add support for specifying a regulator as its power supply.
> > > >
> > > > Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
> > > > ---
> > > >  .../bindings/display/bridge/dumb-vga-dac.txt       |  2 ++
> > >
> > > For the binding,
> > >
> > > Acked-by: Rob Herring <robh@xxxxxxxxxx>
>
> Any comments on this patch from the DRM people?

A comment below.

> ChenYu
>
> > > One code comment below...
> > >
> > > >  drivers/gpu/drm/bridge/dumb-vga-dac.c              | 35 ++++++++++++++++++++++
> > > >  2 files changed, 37 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> > > > index 003bc246a270..164cbb15f04c 100644
> > > > --- a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> > > > @@ -16,6 +16,8 @@ graph bindings specified in Documentation/devicetree/bindings/graph.txt.
> > > >  - Video port 0 for RGB input
> > > >  - Video port 1 for VGA output
> > > >
> > > > +Optional properties:
> > > > +- vdd-supply: Power supply for DAC
> > > >
> > > >  Example
> > > >  -------
> > > > diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c b/drivers/gpu/drm/bridge/dumb-vga-dac.c
> > > > index afec232185a7..59781e031220 100644
> > > > --- a/drivers/gpu/drm/bridge/dumb-vga-dac.c
> > > > +++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c
> > > > @@ -12,6 +12,7 @@
> > > >
> > > >  #include <linux/module.h>
> > > >  #include <linux/of_graph.h>
> > > > +#include <linux/regulator/consumer.h>
> > > >
> > > >  #include <drm/drmP.h>
> > > >  #include <drm/drm_atomic_helper.h>
> > > > @@ -23,6 +24,7 @@ struct dumb_vga {
> > > >       struct drm_connector    connector;
> > > >
> > > >       struct i2c_adapter      *ddc;
> > > > +     struct regulator        *vdd;
> > > >  };
> > > >
> > > >  static inline struct dumb_vga *
> > > > @@ -124,8 +126,33 @@ static int dumb_vga_attach(struct drm_bridge *bridge)
> > > >       return 0;
> > > >  }
> > > >
> > > > +static void dumb_vga_enable(struct drm_bridge *bridge)
> > > > +{
> > > > +     struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
> > > > +     int ret;
> > > > +
> > > > +     if (!IS_ERR(vga->vdd)) {
> > >
> > > if (IS_ERR())
> > >         return;
> > >
> > > ...will save some intentation.
> >
> > I thought about that, though if someone were to add more stuff to
> > this, such as an enable GPIO, they might have to rework it. A standalone
> > block of code would be easier to work with. I'm OK either way though.
> >
> > ChenYu
> >
> > > > +             ret = regulator_enable(vga->vdd);
> > > > +
> > > > +             if (ret) {
> > > > +                     DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
> > > > +                     return;
> > > > +             }
> > > > +     }
> > > > +}
> > > > +
> > > > +static void dumb_vga_disable(struct drm_bridge *bridge)
> > > > +{
> > > > +     struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
> > > > +
> > > > +     if (!IS_ERR(vga->vdd))
> > > > +             regulator_disable(vga->vdd);
> > > > +}
> > > > +
> > > >  static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
> > > >       .attach         = dumb_vga_attach,
> > > > +     .enable         = dumb_vga_enable,
> > > > +     .disable        = dumb_vga_disable,
> > > >  };
> > > >
> > > >  static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
> > > > @@ -169,6 +196,14 @@ static int dumb_vga_probe(struct platform_device *pdev)
> > > >               return -ENOMEM;
> > > >       platform_set_drvdata(pdev, vga);
> > > >
> > > > +     vga->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
> > > > +     if (IS_ERR(vga->vdd)) {
> > > > +             ret = PTR_ERR(vga->vdd);
> > > > +             if (ret == -EPROBE_DEFER)
> > > > +                     return -EPROBE_DEFER;
> > > > +             dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);

A cleaner way would be to set vga->vdd to NULL here, and do:

	int ret = 0;

	if (vga->vdd)
		ret = regulator_enable(vga->vdd);

	if (ret) {
		...
		return;
	}

	/* if a gpio is added later */
	if (vga->gpio)
		ret = gpiod_set_value_cansleep(vga->gpio, 1);

	if (ret) {
		...
		return;
	}
	...

We don't really care what error code is contained in vga->vdd once we have
identified whether we got a regulator or not.

The same thing can be done for ddc too, but that can done left for later.

If you're okay with the suggestion, can you re-spin a patch?

Thanks,
Archit

> > > > +     }
> > > > +
> > > >       vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
> > > >       if (IS_ERR(vga->ddc)) {
> > > >               if (PTR_ERR(vga->ddc) == -ENODEV) {
> > > > --
> > > > 2.9.3
> > >
> > > --
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